This invention relates to rubber and vinyl articles having improved slip coatings and to compositions and methods of providing same. More particularly, the invention relates to rubber and vinyl articles, such as sterile surgeons' gloves, which are provided with an improved slip coating.
It has previously been proposed to provide slip finishes on rubber and vinyl articles such as rubber gloves or girdles by various methods. For example, the surface of a rubber glove can be halogenated with bromine or chlorine to make it slippery. However, this treatment may result in very poor aging properties. Discoloration can begin almost immediately and, within a month, the halogenated surface may become hard and brittle and brown in color. This can be avoided only by taking great care in the halogenation process and even then there is no assurance of obtaining a uniform, sustained, slip film. Waxes and silicone have been used but these provide only a temporary solution as these materials rub off in a very short time. It has further been proposed in U.S. Pat. No. 3,286,011 issued Mar. 18, 1964, and U.S. Pat. No. 3,411,982 issued November 1968, to provide a slip finish comprising a rubber latex and a resin latex. While such coatings reduce the coefficient of friction of the rubber article to a slight extent, it is desirable to further reduce the coefficient of friction. For example, it is desirable to further reduce the coefficient of friction to make it easier to put on and take off a rubber article such as a rubber glove.
In the preparation of rubber articles by dipping into a coagulant solution and then into a rubber latex followed by coagulation of the rubber latex into the desired article, it is usually necessary to first apply to the form a coating of a release agent such as a mold release powder, e.g., talc, diatomaceous earth, etc. or a lubricant type release agent, e.g., glycerine. The reasons for the use of the release agents are (1) to prevent damage to the rubber article when it is stripped from the form and/or (2) to preclude the tendency of the tacky rubber to self adhesion when the article is removed. Use of release agents in the preparation of dipped rubber articles, however, is not without its shortcomings for it naturally leads to adulterated final products which have trapped or otherwise picked up the release agent on the coagulated rubber surface. Nevertheless, the contaminated rubber article is a matter which manufacturers of such articles have had to live with for it has not been possible to obtain these rubber articles in a commercially acceptable form without the use of the release agents.
Another drawback commonly associated with the use of release agents in the manufacture of rubber articles is that the process requires clean up of the residue of the release agent on the mold or form after formation of each and every article, a tedious and time consuming operation.
The same problems necessitating the use of release agents in the formation of rubber article's directly on dipping forms, likewise necessitate the use of release agents in processes such as described in U.S. Pat. No. 3,411,981 to Kavalir, et al. wherein the slip-coated rubber articles are prepared by first providing a release composition onto the form before it is dipped into the rubber latex. In addition to the aforementioned stripping and self-adhesion difficulties, there is a tendency for the slip coating to separate from the rubber substrate when release agents are not utilized in such processes.
Furthermore, in the prior art processes for obtaining slip coatings there has been a tendency for the surface of the articles produced to exhibit streaks.
The foregoing problems were overcome or alleviated by use of the two component synthetic polymer systems described in U.S. Pat. Nos.4,027,060 and 4,082,862. While rubber articles such as gloves produced using the dual polymer component systems and processes of these patents were excellent, they were not without shortcomings. For one, the entire process takes approximately three hours, a process time considered too long by many. Secondly, the removal of the finished gloves from the forms had to be accomplished by stripping under warm water, an inconvenience that further required yet another final drying step. Thirdly, in the prior art processes, coating of the rubber surface with the polymer systems could not be accomplished when the rubber was cured or partially cured. The coating had to be conducted while the rubber was still hydrated. Lastly, it was difficult, if not impossible, to don the finished glove when the hands are wet or damp.
Thus, it is an object of the invention to provide rubber articles containing slip coatings comprised of non-elastomeric materials which when applied to the rubber substrate take on the elastomeric properties of the substrate.
It is also an object of the invention to provide a process for the production of rubber articles which process does not require the use of release agents as a separate and distinct entity and which nevertheless results in a rubber article having a slip coating which has an appreciably lower coefficient of friction than the rubber surface to which it has been applied.
Yet another objective of the invention is to provide a process for the production of rubber articles substantially reduced in process time where such process time is commensurate with or faster than existing commercial cycles.
Another object of the present invention is to provide a process that enables removal of the finished glove from the forms without having to immerse them in warm water.
Still another object of the invention is to provide a process for the manufacture of rubber articles such as gloves which permits coating over cured, partially cured, or uncured (hydrated) rubber and wherein a second deionized leach step is unnecessary.
Yet another object of the invention is to provide rubber or vinyl articles such as gloves which can be donned with wet or damp hands.